Meade ETX-90 AT Telescope Review – Partially Recommended

The ETX-90 Optical Tube

The “new” ETX-90 AT offered by Orion in many ways backtracks from the “Observer” model previously sold, lacking its ability to be detached from the fork mount or the Observer’s jumbo focus knob. It is still a 90mm (3.5”) Maksutov-Cassegrain with a f/13.8 focal ratio and 1250mm focal length, however. The North American-made ETX-90s tend to have a little better optical performance than the JOC/Bresser “Observer” and “Portable Observer” models, and the 2023 ETX-90 AT is no different. The optics feature “UHTC” multicoatings for slightly better light transmission, but with a 90mm aperture and super-long focal length, make no mistake – this is a lunar, planetary, and double star scope.

The ETX-90 has a built-in flip mirror mechanism, which is basically a built-in star diagonal that flips out of the way for a rear port to attach a DSLR camera or a correct image prism for daytime terrestrial viewing. The flip mirror is basically a cheap gimmick, and if it doesn’t line up exactly with the optical axis of the telescope, it makes the views less-than-sharp.

The ETX-90’s extremely “slow” f/13.8 focal ratio offers several benefits, including easy focusing due to the extensive depth of field, sharp star images even when using inexpensive eyepieces, and the ability to achieve high magnifications without extremely short focal length eyepieces or Barlow lenses. A 90mm telescope with near-perfect optics like the ETX-90 can support up to around 180x magnification, or a 7mm focal length eyepiece, before hitting the limit of resolving power. However, the best planetary views are typically found at slightly lower powers, around 100x.

On the other hand, the ETX-90’s small aperture and long focal length significantly impair its ability to observe deep-sky objects. While a 90mm telescope is already limited for deep-sky viewing, refractors and reflectors of a similarly small size with short focal lengths and/or 2″ focusers can still provide a wide field of view suitable for observing large open star clusters and nebulae. The ETX-90’s 1250mm focal length, 1.25″-only eyepiece compatibility, and physical stops within the telescope’s baffle tube restrict the maximum achievable field of view to just 1.25 degrees, or about 2.5 times the angular diameter of the full Moon.

Accessories

The ETX-90 has consistently been accompanied through the years by a 26mm “Super Plossl” 1.25″ eyepiece, and with the 2023 AT version, this is the only ocular supplied. With a 52-degree apparent field of view, this eyepiece provides decent eye relief for glasses-wearers and yields 48x magnification with the ETX-90, resulting in a true field of view just over 1 degree, or roughly twice the angular diameter of the full Moon. While the 26mm Super Plossl delivers sharp views up to the field’s edge, its 52-degree field of view is not particularly immersive, and 48x is not enough for optimal planetary views. At the price the ETX-90 AT presently commands, it’s really inexcusable that another eyepiece or two wasn’t thrown in.

For a finder, the ETX-90 AT includes a standard red dot finder attached to the scope with a non-standard bracket, meaning it’s effectively the only option. However, for the purposes of aiming at bright targets or aligning the GoTo system, it works fine.

A smartphone adapter and “moon filter” are also included with the ETX-90 AT. The simple adapter clamps onto the provided 26mm Plossl and similar eyepieces, allowing for basic lunar photography, though it’s hardly sturdy or high-quality. The “moon filter” is a cheap piece of tinted glass that does little but blur or dim the view, and is hardly necessary anyway.

Mount

The mount for the ETX-90 AT is a computerized alt-azimuth fork design that runs off Meade’s AudioStar. The AudioStar is a primitive GoTo hand controller similar to the AutoStar apart from an additional feature that allows it to speak to you, which you will probably never actually end up wanting to use. It’s also rather unnecessary on the whole, as the ETX-90 is pretty limited in what targets it can show you due to its small aperture and long focal length. 

The ETX-90’s mount also consumes a lot of power. Inserting 8 AA batteries will likely give you one or two nights of observing before the scope drains them. Some sort of reusable/rechargeable battery or power supply is required for the ETX in the long run, unless you can run it exclusively off AC power.

The ETX-90 AT does feature clutches on the mount, which theoretically allow for manual aiming. In practice, however, this is useless, as there is no fine adjustment, and aiming manually will ruin the alignment and accuracy of all GoTo and tracking functions. The scope is attached to Meade’s #884 tripod, a sturdy steel tripod with a built-in “wedge” to convert the scope to an equatorial configuration, but between its lack of fine adjustments and the ETX optical tube and mount being completely unsuitable for deep-sky imaging, there’s not much of a point in using it.

Should I buy a Used Meade ETX-90 AT?

Older Meade ETX-90 models will offer you the same features at a lower price tag and in a more compact form factor, if you must have one. As with any used catadioptric, make sure that the corrector is in one piece (it is essentially irreplaceable) and that the focus moves smoothly, as well as checking that the mirror coatings are in good shape. Maksutov’s secondary “spot” is essentially impossible to recoat, so damage to it is irreversible. If possible, you should also test the mount’s drives and AutoStar/AudioStar systems to make sure it run smoothly.

Alternative Recommendations

Due to its tiny aperture and limited field of view, the Meade ETX-90 AT is simply not capable of revealing details in galaxies, resolving globular star clusters or planetary nebulae, or providing immersive views of larger emission nebulae, even under ideal conditions. This telescope is designed primarily for observing the Moon, planets, and double stars. For anything beyond casual and low-quality deep-sky views, it’s best to consider other options, and there are better Maksutovs available at well below the ETX-90’s sky-high price tag. We’ve picked an assortment of alternative picks for Maksutov-Cassegrains as well as an assortment of larger reflecting telescopes, almost all of which are computerized in some fashion.

Maksutov-Cassegrains

• The Celestron Astro Fi 102 boasts a slightly larger aperture than the ETX-90 while maintaining the sleek Maksutov-Cassegrain optical design and utilizing the stable and user-friendly AstroFi mount and tripod. However, its limited aperture and ultra-long focal length, combined with the 1.25″ eyepiece compatibility, restrict its field of view, further limiting deep-sky observations, much like the ETX-90.
• The Sky-Watcher Virtuoso 90 has the same optical performance as the ETX-90 AT, with a motorized tracking mount and a quality accessory bundle including a solar filter provided. It is a tabletop scope, but can be attached to a suitable sturdy tripod too, and it costs a fraction as much as the ETX.
• The Explore Scientific FirstLight 100mm Mak EQ3 has a slightly larger aperture than the ETX-90, and a simple manual equatorial mount. It’s not perfect, but is a bit more capable, cheaper, and works well.
• The SarBlue Mak70 is smaller than the ETX-90 and all-manual in aiming, but puts up surprisingly good views of bright targets and comes well-equipped with its included accessory bundle.

Reflectors

• The Apertura AD8/Zhumell Z8/Orion SkyLine 8 offers over double the aperture—thus a bit over twice the resolution and 5x the light gathering ability—of the ETX-90 AT, along with a pile of useful accessories and features mounted atop a sturdy and simple Dobsonian mount.
• The Celestron StarSense Explorer 8″ Dobsonian offers computerized pointing assistance through its StarSense Explorer technology connected to your smartphone, as well as a more lightweight and transportable base compared to the AD8/Z8. Although it doesn’t physically adjust the telescope for you, it displays instructions on your smartphone screen via the StarSense Explorer app and adapter. However, it includes few accessories, and collimation of the 8″ model can be cumbersome.
• The Sky-Watcher Virtuoso GTi 150P’s substantially larger aperture than the ETX-90 more than triples light gathering capabilities and nearly doubles resolution. It also features a collapsible tube for easy portability, a pair of high-quality eyepieces, a wide field of view due to its 750mm focal length, and a straightforward tabletop Dobsonian mount. To fully utilize its potential, however, you will need a stable surface or a suitable tripod. In exchange, you’ll enjoy a more expansive field of view than the ETX-90 and the convenience of smartphone or tablet control. Sky-Watcher also offers the Heritage 150P, a completely manual version of the Virtuoso GTi 150P.
• The Sky-Watcher Virtuoso GTi 130P is a marginally smaller variant of the GTi 150P. However, considering the minor differences in dimensions, weight, and cost, we recommend the 150P due to the increased capabilities its extra inch of aperture offers. The 130P is also available in a manual-only format at a lower price, known as the Sky-Watcher Heritage 130P.
• The Celestron Astro Fi 130 features a computerized GoTo mount controlled through your smartphone or tablet and has robust tripod legs. Its 130mm f/5 optics provide views similar to the Sky-Watcher 130P scopes, with the addition of a 2″ focuser, surpassing the ETX-90 in terms of resolving power, achievable field of view, and light gathering capabilities.

Aftermarket Accessory Recommendations

A 32mm Plossl eyepiece will give you a bit lower magnification (39x) and a wider field of view than the ETX-90’s stock 26mm, and it’s the main additional eyepiece we’d recommend for this scope at the low power end.

For medium and high magnifications suitable for lunar, planetary, and double star viewing with the ETX-90 AT, we recommend a 15mm (83x) goldline or redline eyepiece, and a 9mm (139x) goldline/redline as well. Alternatively, eyepieces such as the Agena Starguider or Explore Scientific 62 and 82-degree series oculars work well with the ETX-90, though they are quite a bit more expensive.

A dew shield will help to keep stray light out of the ETX-90 as well as prevent condensation from forming on the corrector plate and reducing glare, and a small rechargeable power supply, such as one from TalentCell, will allow you to forget about running out of AA batteries as well as save you money in the long term if you use the scope frequently.

What can you see with ETX 90?

The ETX-90 excels at observing the Moon and planets, enabling you to see the phases of Mercury and Venus, lunar surface details just a few miles/kilometers in size, Mars’ polar ice caps, Jupiter’s Galilean moons and cloud belts, Saturn’s rings and its brightest moon Titan, as well as Uranus and Neptune as small blue dots. With some effort, you might also glimpse a couple of dark spots on Mars that represent shifting sand patches, Jupiter’s Great Red Spot, and the shadows of Galilean moons during their transit across the planet. Additionally, the ETX-90 may resolve Saturn’s cloud belts, the Cassini division within its rings, and several more of its moons, such as Rhea. The ETX-90’s sharp optics, free from chromatic aberration and diffraction spikes, also make it excellent for splitting double stars, with thousands of vibrant binary stars accessible via the GoTo functionality available with the ETX.

However, the ETX-90 falls short when it comes to detailed views of deep-sky objects like galaxies or globular clusters. At best, you might be able to discern Andromeda or M82 with some difficulty, even under ideal conditions and with a trained eye. Observing galaxies in light-polluted environments can be especially challenging due to the ETX-90’s small aperture. Open star clusters are also less impressive because of the telescope’s limited field of view. While the Orion Nebula is a treat, other nebulae tend to be underwhelming, with the largest ones failing to fit within the field of view and planetary nebulae appearing dim and unresolved if you can manage to see them at all. Globular star clusters need at least a 5″ instrument to resolve individual stars, leaving them as faint fuzzy dots with the ETX-90. For more satisfying and detailed views of most deep-sky objects, we recommend a 4-6″ tabletop Dobsonian or a larger 8″, 10″, or 12″ instrument.

Astrophotography Capabilities

The ETX-90 AT has a relatively small aperture to be useful for planetary imaging; however, satisfactory lunar and planetary images can still be captured using this telescope and a high-speed CMOS planetary camera like the ZWO ASI224MC. Employing a 2x Barlow lens to increase the scope’s image scale to approximately f/28 and a 2500mm focal length is ideal for capturing detailed images of Mars, Jupiter, Saturn, and the Moon’s finer features.

Nonetheless, deep-sky astrophotography remains unattainable with the ETX-90 AT due to the mechanical constraints of the telescope and its mount, as well as its ultra-long focal ratio.